This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine and comprising a nozzle body in which is defined a blind bore, a seating defined adjacent the blind end of the bore, valve means movable axially within the bore, the valve means being shaped for cooperation with the seating and being movable away from the seating to permit fuel to flow past the seating through an outlet orifice and the valve means defining a surface against which fuel under pressure can act to lift the valve means from the seating.
Such nozzles are well known in the art and it is usual for the valve means to be biased into engagement with the seating by a strong spring and for the surface defined by the valve means to have an area such that the force developed on the valve means when fuel under pressure is supplied to the nozzle is sufficient to move the valve means against the force developed by the spring. The valve means therefore lifts from the seating when the fuel pressure attains a predetermined value and therefore the timing of fuel delivery to the engine is dependent upon the rise in the fuel pressure and the manufacturing tolerances of the nozzle.
In order to meet the operating requirements of modern engines it is necessary for the timing of fuel delivery to the engine to be carefully controlled. This is the case particularly with compression ignition engines and the object of the present invention is to provide a fuel injection nozzle of the kind specified in which the initiation of fuel delivery is determined by a control signal which is supplied to the nozzle.